Photolithography (also “optical lithography” or “UV lithography”) is a process used in semiconductor micro-fabrication to pattern parts of a thin film wafer or other substrate. It uses light to transfer a geometric pattern from a photomask (also “mask”) to a light-sensitive chemical “photoresist” (also “resist”) on the substrate. The ability to project a clear image of small features onto the substrate is limited by the wavelength of the light that is used and the ability of a reduction lens system to capture enough diffraction orders from the illuminated mask. Current state-of-the-art photolithography tools use deep ultraviolet (DUV) light from excimer lasers with wavelengths of about 248 and 193 nm, which allow minimum feature sizes down to about 40 nm. A desire to achieve extremely small features on the wafer with high resolution has resulted in extremely large reduction lens systems, which are expensive and unwieldy.
Electron beam lithography (also “e-beam lithography”) is another process used in semiconductor micro-fabrication to pattern parts of a substrate. E-beam lithography emits a beam of electrons in a patterned fashion across the substrate covered with resist to selectively expose the resist. As such, e-beam lithography does not utilize a photomask to create a pattern and is therefore is not limited by the diffraction limit of the exposing light penetrating though the photomask. As a result, e-beam lithography does not require the extremely large reduction lens systems utilized in optical lithography. However, e-beam lithography typically requires a long exposure time and is thus limited in its throughput capability, which renders e-beam lithography not cost effective for many manufacturing processes. Further, e-beam exposure can be problematic when directly patterning on magnetic films because of undesirable interactions between the electron charges and the magnetic film.